Parasitic losses in a typical front engine accessory drive (FEAD) system of a vehicle can contribute to higher fuel consumption. The initial system belt tension is one of the main contributors to parasitic power losses. In heavy truck applications (for example, on highway class 8 trucks), it is often the power requirements of the engine fan that drive the required belt tension. (For example in large transport trucks, a typical large diameter belt driven cooling fan can absorb somewhere in the range of 50 to 75 horsepower directly from the engine crankshaft power output via the engine accessory belt drive, and can weigh in excess of 20 pounds for the clutch mechanism alone.) At the same time, the engine fan is not always needed to cool the engine. Consequently, many applications use a pneumatically controlled ON-OFF fan clutch. When the fan is not required to cool the engine, the clutch is controlled to decouple the fan from the engine accessory belt drive. However, when a typical passive tensioner is used to maintain belt tension in a typical FEAD system, the belt tension remains high even when the fan is off because of the relatively high spring rate used in the tensioner spring which is needed to prevent contact of the belt tensioner arm against its load stop when the fan is on. If the belt tension during these times can be reduced, the fuel consumption can also be reduced. FIGS. 1a and 1b show the tensioner torque requirements for a front engine accessory drive (FEAD) system in order to prevent slip in situations where the fan is off and the fan is on. The parasitic losses incurred during operation of the engine include belt losses which are directly related to the movement (e.g. flexing) of the belt itself, and friction losses which result from friction in the bearings supporting the shafts of the accessories and friction in the seals that are engaged with the accessory shafts. Additionally there are crankshaft losses. During vehicle use, the engine must overcome these losses (and other losses) and the remaining torque is the torque that is available for driving the vehicle. The higher the belt tension, the higher the parasitic losses.